112 M M. Junker & Dufrenoy, on the Tin, Sfc. 



magnesia and common opal, (quartz resinite) in the serpen- 

 tine of Piedmont. 



It should be remarked that few of these veins are metal- 

 liferous, and that out of more than ten cut by the trench, 

 two only afforded oxide of tin, and those irregularly and 

 without continuity. 



[Here the authors describe veins bent in different di- 

 rections.] 



The trench was cut for some metres in the quartzose 

 mica slate covering the granite, but nothing was discovered 

 in this part of it. 



Many of the veins which cut the rocks covered by the 

 tide, and especially those near the Tombeau d'Almanzor, 

 having been found to be stanniferous, we attacked them 

 with the intention of discovering the mode of occurrence of 

 the ore, &c. 



We found that the oxide of tin occurred in nests and 

 veins, accompanied by quartz and mica, often decomposed. 

 In nests when the quartz was abundant ; in veins on the 

 contrary, when mica predominated ; in the latter case the 

 tin is in greater quantity, and it is seen to augment the 

 more the mica and granite are decomposed ; the tin is then 

 in a loose and friable state. 



